The units for N must represent power; Newton is the MKS unit of force, not power, and KWH is a unit of energy, not power.

No rolling resistance is a force, to compute the power needed to over come it you need to know how fast the car is going.

N = newtons the force resisting motion.

There are several other rolling resistance formulas out there in various engineering texts and some books on aerodynamics, mention it as well.

The best way to determine it is to use low speed coast down information where the dominant form of drag is rolling resistance rather than aerodynamic drag.

Larry